Yukon Kuskokwim Rapid Ecoregional Assessment (REA)

REA Status The Yukon Kuskokwim REA was initiated in August 2012. It has been completed and peer reviewed and will soon be available to the public. The Memos and Reports section provide access to the REA data for this ecoregion.

Location and Setting The Yukon Kuskokwim REA in Interior Alaska encompasses three distinct ecoregions: the Yukon Lowlands, the Kuskokwim Mountains, and the Lime Hills (YKL). Combined, these ecoregions total nearly 41 million acres managed by seven major landowners.

The Yukon Lowlands are part of an extensive wetland system associated with the lower stretches of the Yukon and Koyukuk rivers in the western regions of Interior Alaska. White spruce and balsam poplar line the major rivers. They surround tall stands of alder and willow which grow throughout the floodplains and river bars. Wet sedge meadows and aquatic vegetation fill sloughs and oxbow ponds. Black spruce woodlands, birch-ericaceous shrubs and sedge-tussock bogs cover areas underlain with permafrost.

The Kuskokwim Mountains are old, low, rolling mountains south and east of the Yukon Lowlands. These mountains are underlain with thin to moderately thick permafrost. White spruce, white birch, and trembling aspen cover the uplands and black spruce and tamarack fill the lowlands.

The Lime Hills are glacially dissected mountains descending from the west side of the Alaska Range and south of the Kuskokwim Mountains. This region’s heavy glaciation resulted in sharp mountain ridges with steep headwalls and broad U-shaped valleys. Shrub communities of willow, birch and alder dominate the vegetation. Valley bottoms and mountains slopes are spruce forests and woodlands.

These three ecoregions support large wildlife populations of moose, bear, beavers, furbearers and scattered caribou herds; waterfowl; and, important runs of sockeye, Chinook, chum and coho salmon in the larger rivers.

Conservation Elements Conservation elements are renewable resources of high conservation interest within an ecoregion. This REA will assess the current condition and forecasted future condition of two types of conservation elements:

“Coarse-filter” conservation elements, which typically include all of the major ecosystem types within the assessment landscape, and represent all of the predominant natural ecosystem functions and services in the ecoregions;

and “Fine-filter” conservation elements, which complement the first set of elements by including a limited subset of focal species assemblages and individual species.

Thirty conservation elements were selected for assessment in this REA: nine coarse-filter terrestrial elements, five coarse-filter aquatic elements, nine fine-filter terrestrial elements, and seven fine-filter aquatic elements. See the Memos and Reports section to view Memorandum 1, which provides the full list of conservation elements.

Change Agents A key purpose of this REA is to understand the influences of significant widespread change agents on the natural resources of the ecoregions in the Yukon Kuskokwim REA. Change agents are features or phenomena that have the potential to affect the size, condition, and landscape context of conservation elements. The following change agents will be assessed:

Data, Maps, and Models Geospatial data, maps, and models used in and produced by the REAs will be made available to the public upon final completion of each individual assessment.

Memos and Reports For each REA, there is a series of memos which are supplemental documents to the final report. Memos document the major tasks and decision points made during the assessments and provide pertinent background information necessary to understand the justification and methods used during the assessment. As memos and the final report are completed, they can be downloaded through the table below.